look for nillkin or jekod covers for Mi2 on ebay: IMHO they are the best
I've one of these (a nillkin one) and It's very well made, not so expensive in comparison with others, but superior quality
---------------------------------------------------
sciphone.fr (french) or ibuygou.com (chinese) are good and reliable web sites for Mi2 accessories
or simply you can search on ebay or aliexpress
Regards